To get rid of this error message all you need to do 90% of the Time is just go to "Options" to "Enviromental Settings" to "VFAPI Plugins" and Raise the Priority of the "Direct Show Multi-Media File Reader" to "2"....This should get your files loaded as long as you have the Codec installed which you would need to have just to watch the file in Media Player.....

I have now encountered an entirely different problem to do with TMPGEnc DVD Author. It works swimmingly all the way up to encoding and processing the files but when I look into the ts_video folder there is nothing there! Even though it has gone through the processing stage without a single problem?!

Well Tmpgenc DVD author doesn"t do any encodeing unless you have the new AC3 Plugin in which case it can encode the audio to AC3 but it does Proscess the files to Vob files in the Video_TS Folder...I have no idea why it is not working ,I personally do not use Tmpgenc DVD author much Cuz it is to Basic and is lacking in Features..You can allways try a different program to author the DVD ,Maybe try "DVD-Lab" it is a More High end program but Costs about the same you can download a 30 day fully woring demo at :
"http://www.mediachance.com/dvdlab/"